Phase F: Customer/Vendor Statements, Payment Terms Parser, Tax Rates

F1: GetCustomerStatementAsync/GetVendorStatementAsync on IFinancialReportService;
    StatementLineDto; CustomerStatementDto/VendorStatementDto; Statement action on
    CustomersController + VendorsController; Statement views + PDF download via
    StatementPdfHelper (QuestPDF); Statement button on Customer/Vendor Details pages.

F2: PaymentTermsParser static helper (CalculateDueDate, ParseEarlyPaymentDiscount);
    EarlyPaymentDiscountPercent/Days on Invoice entity; GetCustomerPaymentTerms AJAX
    endpoint on InvoicesController auto-populates Terms + due date on customer select;
    early payment discount notice on Invoice Create.

F3: TaxRate entity (Name/Rate/State/IsDefault/IsActive, tenant-filtered);
    IUnitOfWork.TaxRates + UnitOfWork + ApplicationDbContext; TaxRatesController
    (Index/Create/Edit/Delete/ToggleActive, CompanyAdminOnly); GetTaxRateForCustomer
    AJAX endpoint; Tax Rates in Settings gear menu.

Also fixes AddVendorCredits migration: VendorCreditApplications FKs changed from
CASCADE to NoAction to resolve SQL Server error 1785 (multiple cascade paths).
Migration: AddPaymentTermsAndTaxRates applied locally; 200/200 unit tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/VendorsController.cs

@@ -7,9 +7,11 @@ using Microsoft.AspNetCore.Mvc.Rendering;
 using Microsoft.EntityFrameworkCore;
 using PowderCoating.Application.DTOs.Common;
 using PowderCoating.Application.DTOs.Vendor;
+using PowderCoating.Application.Interfaces;
 using PowderCoating.Core.Entities;
 using PowderCoating.Core.Enums;
 using PowderCoating.Core.Interfaces;
+using PowderCoating.Web.Helpers;
 
 namespace PowderCoating.Web.Controllers;
 
@@ -27,17 +29,23 @@ public class VendorsController : Controller
     private readonly IMapper _mapper;
     private readonly UserManager<ApplicationUser> _userManager;
     private readonly ILogger<VendorsController> _logger;
+    private readonly IFinancialReportService _financialReports;
+    private readonly ITenantContext _tenantContext;
 
     public VendorsController(
         IUnitOfWork unitOfWork,
         IMapper mapper,
         UserManager<ApplicationUser> userManager,
-        ILogger<VendorsController> logger)
+        ILogger<VendorsController> logger,
+        IFinancialReportService financialReports,
+        ITenantContext tenantContext)
     {
         _unitOfWork = unitOfWork;
         _mapper = mapper;
         _userManager = userManager;
         _logger = logger;
+        _financialReports = financialReports;
+        _tenantContext = tenantContext;
     }
 
     /// <summary>
@@ -377,6 +385,29 @@ public class VendorsController : Controller
 
     /// <summary>
     /// Populates <c>ViewBag.ExpenseAccounts</c> with active Expense, Cost of Goods, and Asset accounts
+    /// <summary>
+    /// Displays or downloads a dated activity statement for a vendor.
+    /// </summary>
+    [HttpGet]
+    public async Task<IActionResult> Statement(int id, DateTime? from, DateTime? to, bool pdf = false)
+    {
+        var companyId = _tenantContext.GetCurrentCompanyId() ?? 0;
+        var fromDate  = from ?? new DateTime(DateTime.Today.Year, DateTime.Today.Month, 1);
+        var toDate    = to   ?? DateTime.Today;
+
+        var dto = await _financialReports.GetVendorStatementAsync(companyId, id, fromDate, toDate);
+
+        if (pdf)
+        {
+            var bytes = StatementPdfHelper.Generate(
+                dto.VendorName, dto.CompanyName, null,
+                dto.From, dto.To, dto.OpeningBalance, dto.Lines, dto.ClosingBalance, isVendor: true);
+            return File(bytes, "application/pdf", $"Statement-{dto.VendorName}-{toDate:yyyyMMdd}.pdf");
+        }
+
+        return View(dto);
+    }
+
     /// for the vendor's default expense account dropdown. All three account types are included because
     /// vendor bills can legitimately be coded to COGS (powder, materials) or asset accounts (equipment
     /// purchases) in addition to regular operating expenses. A "— None —" placeholder is prepended so